Groundwater contributions to surface water in the Assiniboine Delta Aquifer (ADA): A water quantity and quality perspective
Citation
Danielescu, S., Barbecot, F., Morand, V. (2021). Groundwater contributions to surface water in the Assiniboine Delta Aquifer (ADA): A water quantity and quality perspective. Journal of Great Lakes Research, [online] 47(3), 788-797. http://dx.doi.org/10.1016/j.jglr.2020.11.002
Plain language summary
In the Lake Winnipeg Basin (LWB), at both basin and regional scales, the role of groundwater as a source of nutrient and contaminant fluxes to Lake Winnipeg is not well known. During 2018, surface water and groundwater samples were collected from various locations across the largest sand and gravel aquifer (Assiniboine Delta Aquifer [ADA]; 3800 km2) in the LWB as well as from surface water courses flowing above this aquifer. The samples collected during spring and fall were analyzed for anions and cations as well as for a series of isotopic and geochemical tracers (e.g. water isotopes, carbon 14, artificial sweeteners, pesticides, etc.). The results suggest that groundwater has similar chemical composition with the small watercourses flowing above the ADA and both are significantly different than the chemical composition of the main watercourse flowing above the aquifer (Assiniboine River [AR]). The study found that that groundwater plays a significant role at local scale in controlling both the flow and the chemical composition of the AR tributaries. Groundwater age tracers indicate a relatively large travel time of water in the subsurface (up to 2400 years).
Abstract
In the Lake Winnipeg Basin (LWB), at both basin and regional scales, there are currently gaps regarding the significance of groundwater as a mediator of nutrient and contaminant fluxes to Lake Winnipeg. During 2018, surface water and groundwater samples were collected from various locations across the largest sand and gravel aquifer (Assiniboine Delta Aquifer [ADA]; 3800 km2) in the LWB as well as from surface water courses flowing above this aquifer. The samples collected during spring and fall were analyzed for anions and cations as well as for a series of isotopic and geochemical tracers (e.g. water isotopes, carbon 14, artificial sweeteners, pesticides, etc.). The results reveal that groundwater and the small watercourses flowing above the ADA have a similar chemical composition, which is in contrast with the chemical composition of the main watercourse flowing above the aquifer (Assiniboine River [AR]). When corroborated with stream discharge measurements this indicates that groundwater plays a significant role at local scale in controlling both the flow and the chemical composition of the AR tributaries. Nitrate showed low to non-detectable concentrations in both groundwater and surface water. With respect to groundwater, this could be related to the reducing conditions in the deeper aquifer in conjunction with relatively large groundwater travel times of up to 2400 years.